Illustrator is a vector drawing program. It is often used to draw illustrations, cartoons, diagrams, charts and logos. Unlike bitmap images that stores information in a grid of dots, Illustrator uses mathematical equations to draw out the shapes. This makes vector graphics scalable without the...
ou can't. That would be trying to put a square plug in a round hole. JPEG is file format for images. HTML (hypertext mark up language) is file detailing how to display images of JPG, GIF, whatever, text on a webpage.
CSS is a style language that defines layout of HTML documents. For example, CSS covers fonts, colours, margins, lines, height, width, background images, advanced positions and many other things.